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Duloxetine, a serotonin and norepinephrine reuptake inhibitor (SNRI), is the best-established treatment for painful chemotherapy-induced peripheral neuropathy (CIPN). While it is only effective in little more than half of patients, our ability to predict patient response remains incompletely understood. Given that stress exacerbates CIPN, and that the therapeutic effect of duloxetine is thought to be mediated, at least in part, via its effects on adrenergic mechanisms, we evaluated the contribution of neuroendocrine stress axes, sympathoadrenal and hypothalamic-pituitary-adrenal (HPA), to the effect of duloxetine in preclinical models of oxaliplatin- and paclitaxel-induced CIPN. Systemic administration of duloxetine, which alone had no effect on nociceptive threshold, both and mechanical hyperalgesia associated with oxaliplatin- and paclitaxel-CIPN. It more robustly attenuated oxaliplatin CIPN in male rats, while it was more effective for paclitaxel CIPN in females. Gonadectomy attenuated these sex differences in the effect of duloxetine. To assess the role of neuroendocrine stress axes in the effect of duloxetine on CIPN, rats of both sexes were submitted to adrenalectomy combined with fixed level replacement of corticosterone and epinephrine. While CIPN, in these rats, was of similar magnitude to that observed in adrenal-intact animals, rats of neither sex, responded to duloxetine. Furthermore, duloxetine blunted an increase in corticosterone induced by oxaliplatin, and prevented the exacerbation of CIPN by sound stress. Our results demonstrate a role of neuroendocrine stress axes in duloxetine analgesia (anti-hyperalgesia) for the treatment of CIPN.Painful chemotherapy-induced peripheral neuropathy (CIPN) is a debilitating dose-dependent and therapy limiting side-effect of many of the cytostatic drugs used to treat cancer (Argyriou et al., 2010; Marmiroli et al., 2017). Duloxetine is the only treatment for CIPN currently recommended by the American Society of Clinical Oncology (Hershman et al., 2014). In the present study, focused on elucidating mechanisms mediating the response of oxaliplatin- and paclitaxel-induced painful peripheral neuropathy to duloxetine, we demonstrate a major contribution to its effect of neuroendocrine stress axis function. These findings, which parallel the clinical observation that stress may impact response of CIPN to duloxetine (Taylor et al., 2007), open new approaches to the treatment of CIPN and other stress-associated pain syndromes.
Learn More >Irritable bowel syndrome (IBS) is a chronic gastrointestinal disorder characterized by abdominal pain and altered bowel habit that affects ~11% of the global population. Over the past decade, preclinical and clinical studies have revealed a variety of novel mechanisms relating to the visceral analgesic effects of guanylate cyclase-C (GC-C) agonists. Here we discuss the mechanisms by which GC-C agonists target the GC-C/cyclic guanosine-3',5'-monophosphate (cGMP) pathway, resulting in visceral analgesia as well as clinically relevant relief of abdominal pain and other sensations in IBS patients. Due to the preponderance of evidence we focus on linaclotide, a 14-amino acid GC-C agonist with very low oral bioavailability that acts within the gut. Collectively, the weight of experimental and clinical evidence supports the concept that GC-C agonists act as peripherally acting visceral analgesics.
Learn More >Many new first-in-class drugs for neuroscience indications have been introduced in the past decade including new treatments for migraine, amyotrophic lateral sclerosis, depression, and multiple sclerosis. However, significant unmet patient needs remain in areas such as chronic pain, neurodegeneration, psychiatric diseases, and epilepsy. This review summarizes some of the advanced clinical compounds for these indications. Additionally, current opportunities and challenges that remain with respect to genetic validation, biomarkers, and translational models are discussed.
Learn More >TRP channels play a central role in the transduction of thermal and nociceptive stimuli by free nerve endings. Most of the research on these channels has been conducted in vitro or in vivo in non-human animals and translation of these results to humans must account for potential experimental biases and interspecific differences. This study aimed at evaluating the involvement of TRPM8, TRPA1 and TRPV1 channels in the transduction of heat and cold stimuli by the human thermonociceptive system. For this purpose, we evaluated the effects of topical agonists of these three channels (menthol, cinnamaldehyde and capsaicin) on the event-related brain potentials (ERPs) elicited by phasic thermal stimuli (target temperatures: 10°C, 42°C, and 60°C) selected to activate cold Aδ thermoreceptors, warm sensitive C thermoreceptors and heat sensitive Aδ polymodal nociceptors. Sixty-four participants were recruited, 16 allocated to each agonist solution group (20% menthol, 10% cinnamaldehyde, 0.025% capsaicin and 1% capsaicin). Participants were treated sequentially with the active solution on one forearm and vehicle only on the other forearm for 20 minutes. Menthol decreased the amplitude and increased the latency of cold and heat ERPs. Cinnamic aldehyde decreased the amplitude and increased the latency of heat but not cold ERPs. Capsaicin decreased the amplitude and increased the latency of heat ERPs and decreased the amplitude of the N2P2 complex of the cold ERPs without affecting the earlier N1 wave or the latencies of the peaks. These findings are compatible with previous evidence indicating that TRPM8 is involved in innocuous cold transduction and that TRPV1 and TRPA1 are involved in noxious heat transduction in humans.
Learn More >Opioid analgesics remain widely used for pain treatment despite the related serious side effects. Some of those, such as opioid tolerance and opioid-induced hyperalgesia may be at least partially due to modulation of opioid receptors (OR) function at nociceptive synapses in the spinal cord dorsal horn. It was suggested that increased release of different chemokines under pathological conditions may play a role in this process. The goal of this study was to investigate the crosstalk between the µOR, transient receptor potential vanilloid 1 (TRPV1) receptor and C-C motif ligand 2 (CCL2) chemokine and the involvement of spinal microglia in the modulation of opioid analgesia.
Learn More >Background The Centers for Disease Control and Prevention (CDC) issued guidelines and certain healthcare payers have made pharmacy coverage changes (PCC) focusing on regulating prescription opioids. Aim We evaluated differences in the rate of first-time opioid fills at doses ≥ 50 morphine milligram equivalents (MME)/day and first-time opioid fills with benzodiazepine fill overlap following the CDC guidelines and following a PCC between provider types, geographic locations, and insurance types. Method We used OptumLabs® Data Warehouse claims data between 2014 and 2018. Subjects were opioid naïve non-cancer care patients, 18 years and older who had an identified chronic pain condition ICD diagnosis within 2 weeks prior to their first-time opioid fill. We used multiple treatment period segmented regression analysis with interaction terms to test the differences between primary care providers (PCPs) and specialist providers (SPs), urban and rural primary care service areas (PCSAs), and Medicare Advantage (MA) and commercially insured patients (CIPs) in their first-time opioid fill patterns. Results Prescribing first-time opioid fills at doses ≥ 50MME/day declined following the CDC guidelines and PCC, the decline was greater among SPs than PCPs and in rural PCSAs than urban PCSAs. Also, following the CDC guidelines, the decline was greater among MA patients however following the PCC the decline was greater among CIPs. There were no differences in rate of first-time opioid fill with benzodiazepine overlap between groups. Conclusion Responses to the CDC opioid guidelines and a PCC differed between PCPs and SPs, urban and rural PCSAs, and when prescribing to MA and CIPs. Understanding these differences is important to help inform future guidelines.
Learn More >Implanted spinal neuromodulation (SNMD) techniques are used in the treatment of refractory chronic pain. They involve the implantation of electrodes around the spinal cord (spinal cord stimulation (SCS)) or dorsal root ganglion (dorsal root ganglion stimulation (DRGS)), and a pulse generator unit under the skin. Electrical stimulation is then used with the aim of reducing pain intensity.
Learn More >Chronic pain, pain catastrophizing, and mental health disorders such as anxiety or depression frequently occur together and are challenging to treat. To help understand the relationship between these conditions, we sought to identify distinct phenotypes associated with worse pain and function. In a cohort of people with chronic pain on opioids seeking medical cannabis in New York, we conducted latent class analysis to identify clusters of participants based on pain catastrophizing and mental health symptoms of depression, anxiety, post-traumatic stress disorder (PTSD) and attention deficit/hyperactivity disorder (ADHD). We then compared clusters with respect to sociodemographic and clinical characteristics using descriptive statistics. Among 185 participants, we identified four discrete groups: low pain catastrophizing and low mental health symptoms (49% of participants), low pain catastrophizing and ADHD-predominant mental health symptoms (11%), high pain catastrophizing and anxiety-predominant mental health symptoms (11%), and high pain catastrophizing and high mental health symptoms (30%). The group with high pain catastrophizing and high mental health symptoms had the worst pain intensity and interference, disability, insomnia, and quality of life, compared to the two groups with lower pain catastrophizing, though not all differences were statistically significant. Our findings highlight the importance of identifying and addressing pain catastrophizing in patients with comorbid chronic pain and mental health symptoms.
Learn More >This study aimed to explore the independent risk factors for postherpetic neuralgia (PHN).
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